APOBEC3 (apolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3) proteins are cellular DNA deaminases that restrict a broad spectrum of lentiviruses. This process is counteracted by Vif (viral infectivity factor) of lentiviruses, which binds APOBEC3s and promotes their degradation. CBF-β (core binding factor subunit β) is an essential co-factor for the function of human immunodeficiency virus type 1 Vif to degrade human APOBEC3s. However, the requirement for CBF-β in Vif-mediated degradation of other mammalian APOBEC3 proteins is less clear. Here, we determined the sequence of feline CBFB and performed phylogenetic analyses. These analyses revealed that mammalian CBFB is under purifying selection. Moreover, we demonstrated that CBF-β is dispensable for feline immunodeficiency virus Vif-mediated degradation of APOBEC3s of its host. These findings suggested that primate lentiviruses have adapted to use CBF-β, an evolutionary stable protein, to counteract APOBEC3 proteins of their hosts after diverging from other lentiviruses.
Yellow fever virus (YFV)-17D is an empirically developed, highly effective live-attenuated vaccine that has been administered to human beings for almost a century. YFV-17D has stood as a paradigm for a successful viral vaccine, and has been exploited as a potential virus vector for the development of recombinant vaccines against other diseases. In this study, a DNA-launched YFV-17D construct (pBeloBAC-FLYF) was explored as a new modality to the standard vaccine to combine the commendable features of both DNA vaccine and live-attenuated viral vaccine. The DNA-launched YFV-17D construct was characterized extensively both in cell culture and in mice. High titres of YFV-17D were generated upon transfection of the DNA into cells, whereas a mutant with deletion in the capsid-coding region (pBeloBAC-YF/ΔC) was restricted to a single round of infection, with no release of progeny virus. Homologous prime–boost immunization of AAD mice with both pBeloBAC-FLYF and pBeloBAC-YF/ΔC elicited specific dose-dependent cellular immune response against YFV-17D. Vaccination of A129 mice with pBeloBAC-FLYF resulted in the induction of YFV-specific neutralizing antibodies in all vaccinated subjects. These promising results underlined the potential of the DNA-launched YFV both as an alternative to standard YFV-17D vaccination and as a vaccine platform for the development of DNA-based recombinant YFV vaccines.
Crimean–Congo hemorrhagic fever virus (CCHFV) is a member of the genus Nairovirus of the family Bunyaviridae, that can cause severe haemorrhagic fever in humans, with mortality rates above 30 %. CCHFV is the most widespread of the tick-borne human viruses and it is endemic in areas of central Asia, the Middle East, Africa and southern Europe. Its viral genome consists of three negative-sense RNA segments. The large segment (L) encodes a viral RNA-dependent RNA polymerase (L protein), the small segment (S) encodes the nucleocapsid protein (N protein) and the medium segment (M) encodes the envelope proteins. The N protein of bunyaviruses binds genomic RNA, forming the viral ribonucleoprotein (RNP) complex. The L protein interacts with these RNP structures, allowing the initiation of viral replication. The N protein also interacts with actin, although the regions and specific residues involved in these interactions have not yet been described. Here, by means of immunoprecipitation and immunofluorescence assays, we identified the regions within the CCHFV N protein implicated in homo-oligomerization and actin binding. We describe the interaction of the N protein with the CCHFV L protein, and identify the N- and C-terminal regions within the L protein that might be necessary for the formation of these N–L protein complexes. These results may guide the development of potent inhibitors of these complexes that could potentially block CCHFV replication.
Rotavirus (RV) A is a very common cause of acute diarrhoea in infants and young children worldwide. Most human strains are classified into two major Wa-like and DS-1-like genotype constellations, whilst a minor third strain, AU-1, was described in 1989 among human RV isolates from Japan. AU-1 demonstrates a high degree of homology to a feline RV, FRV-1, which suggests interspecies transmission of feline RV. However, there has been no subsequent report of RVs possessing the AU-1 genotype throughout all 11 genes of the genome. Between March 1997 and December 1999, 157 RV-positive stool samples were collected from Brazilian children, and 16 of the RVs (10.2 %) were P genotype. We analysed eight strains by almost full-genome sequencing. These eight strains were divided into two groups: five AU-1-like and three Wa-like strains. Four of the five AU-1-like strains had the AU-1-like genotype constellation throughout the 11 genes. The remaining AU-1-like strain was considered to be a reassortant strain comprosed of nine, two and one genes from the AU-1-like, Wa-like and G9 strains, respectively. The three Wa-like strains were considered to be reassortants comprising seven to eight genes and three to four genes from Wa-like and non-Wa-like strains, respectively. This report of human G3P RV strains possessing the AU-1 genotype constellation throughout all genes demonstrates the stability and infectivity of the AU-1-like strain with its original genotype over distance and time.
Neutralizing antibodies (NAbs) are believed to comprise an essential component of the protective immune response induced by vaccines against feline immunodeficiency virus (FIV) and human immunodeficiency virus (HIV) infections. However, relatively little is known about the role of NAbs in controlling FIV infection and subsequent disease progression. Here, we present studies where we examined the neutralization of HIV-luciferase pseudotypes bearing homologous and heterologous FIV envelope proteins (n = 278) by sequential plasma samples collected at 6 month intervals from naturally infected cats (n = 38) over a period of 18 months. We evaluated the breadth of the NAb response against non-recombinant homologous and heterologous clade A and clade B viral variants, as well as recombinants, and assessed the results, testing for evidence of an association between the potency of the NAb response and the duration of infection, CD4+ T lymphocyte numbers, health status and survival times of the infected cats. Neutralization profiles varied significantly between FIV-infected cats and strong autologous neutralization, assessed using luciferase-based in vitro assays, did not correlate with the clinical outcome. No association was observed between strong NAb responses and either improved health status or increased survival time of infected animals, implying that other protective mechanisms were likely to be involved. Similarly, no correlation was observed between the development of autologous NAbs and the duration of infection. Furthermore, cross-neutralizing antibodies were evident in only a small proportion (13 %) of cats.
Human metapneumovirus (hMPV) and respiratory syncytial virus, its close family member, are two major causes of lower respiratory tract infection in the paediatric population. hMPV is also a common cause of worldwide morbidity and mortality in immunocompromised patients and older adults. Repeated infections occur often, demonstrating a heavy medical burden. However, there is currently no hMPV-specific prevention treatment. This review focuses on the current literature on hMPV vaccine development. We believe that a better understanding of the role(s) of viral proteins in host responses might lead to efficient prophylactic vaccine development.
Herpes simplex virus type 1 (HSV-1; human herpesvirus 1) and varicella-zoster virus (VZV; human herpesvirus 3) are human neurotropic alphaherpesviruses that cause lifelong infections in ganglia. Following primary infection and establishment of latency, HSV-1 reactivation typically results in herpes labialis (cold sores), but can occur frequently elsewhere on the body at the site of primary infection (e.g. whitlow), particularly at the genitals. Rarely, HSV-1 reactivation can cause encephalitis; however, a third of the cases of HSV-1 encephalitis are associated with HSV-1 primary infection. Primary VZV infection causes varicella (chickenpox) following which latent virus may reactivate decades later to produce herpes zoster (shingles), as well as an increasingly recognized number of subacute, acute and chronic neurological conditions. Following primary infection, both viruses establish a latent infection in neuronal cells in human peripheral ganglia. However, the detailed mechanisms of viral latency and reactivation have yet to be unravelled. In both cases latent viral DNA exists in an ‘end-less’ state where the ends of the virus genome are joined to form structures consistent with unit length episomes and concatemers, from which viral gene transcription is restricted. In latently infected ganglia, the most abundantly detected HSV-1 RNAs are the spliced products originating from the primary latency associated transcript (LAT). This primary LAT is an 8.3 kb unstable transcript from which two stable (1.5 and 2.0 kb) introns are spliced. Transcripts mapping to 12 VZV genes have been detected in human ganglia removed at autopsy; however, it is difficult to ascribe these as transcripts present during latent infection as early-stage virus reactivation may have transpired in the post-mortem time period in the ganglia. Nonetheless, low-level transcription of VZV ORF63 has been repeatedly detected in multiple ganglia removed as close to death as possible. There is increasing evidence that HSV-1 and VZV latency is epigenetically regulated. In vitro models that permit pathway analysis and identification of both epigenetic modulations and global transcriptional mechanisms of HSV-1 and VZV latency hold much promise for our future understanding in this complex area. This review summarizes the molecular biology of HSV-1 and VZV latency and reactivation, and also presents future directions for study.
The reverse zoonotic events that introduced the 2009 pandemic influenza virus into pigs have drastically increased the diversity of swine influenza viruses in Europe. The pandemic potential of these novel reassortments is still unclear, necessitating enhanced surveillance of European pigs with additional focus on risk assessment of these new viruses. In this study, four European swine influenza viruses were assessed for their zoonotic potential. Two of the four viruses were enzootic viruses of subtype H1N2 (with avian-like H1) and H3N2, and two were new reassortants, one with avian-like H1 and human-like N2 and one with 2009 pandemic H1 and swine-like N2. All viruses replicated to high titres in nasal wash and nasal turbinate samples from inoculated ferrets and transmitted efficiently by direct contact. Only the H3N2 virus transmitted to naïve ferrets via the airborne route. Growth kinetics using a differentiated human bronchial epithelial cell line showed that all four viruses were able to replicate to high titres. Further, the viruses revealed preferential binding to the 2,6-α-silalylated glycans and investigation of the antiviral susceptibility of the viruses revealed that all were sensitive to neuraminidase inhibitors. These findings suggested that these viruses have the potential to infect humans and further underline the need for continued surveillance as well as biological characterization of new influenza A viruses.
Rift Valley fever virus (RVFV) is the most pathogenic member of the genus Phlebovirus within the family Bunyaviridae, and can cause severe disease in humans and livestock. Until recently, limited information has been published on the cellular host response elicited by RVFV, particularly in macrophages and dendritic cells, which play critical roles in stimulating adaptive and innate immune responses to viral infection. In an effort to define the initial response of host immunomodulatory cells to infection, primary mouse bone marrow derived macrophages (BMDM) were infected with the pathogenic RVFV strain ZH501, or attenuated strains MP-12 or MP-12 based Clone13 type (rMP12-C13 type), and cytokine secretion profiles examined. The secretion of T helper (Th)1-associated antiviral cytokines, chemokines and various interleukins increased rapidly after infection with the attenuated rMP12-C13 type RVFV, which lacks a functional NSs virulence gene. In comparison, infection with live-attenuated MP-12 encoding a functional NSs gene appeared to cause a delayed immune response, while pathogenic ZH501 ablates the immune response almost entirely. These data demonstrate that NSs can inhibit components of the BMDM antiviral response and supports previous work indicating that NSs can specifically regulate the type I interferon response in macrophages. Furthermore, our data demonstrate that genetic differences between ZH501 and MP-12 reduce the ability of MP-12 to inhibit antiviral signalling and subsequently reduce virulence in BMDM, demonstrating that viral components other than NSs play a critical role in regulating the host response to RVFV infection.
The open reading frame 45 (ORF45) of the Kaposi's sarcoma-associated herpesvirus (KSHV) is an immediate-early phosphorylated tegument protein critical for viral escape from host immune surveillance. Its expression is upregulated by the viral replication and transcription activator (RTA), a key protein that controls the switch from latency to lytic replication. We report here that ORF45 expression was not only upregulated by RTA, but ORF45 could also be degraded by RTA in a proteasome-dependent manner. The ORF45 was activated by RTA via activation of the ORF45 promoter, and the promoter region from nt 69 271 to nt 69 026 was involved. In chronic KSHV infected TRE-BCBL-1 RTA cells, the endogenous ORF45 protein increased dramatically after the induction of RTA expression, but then decreased rapidly after 8 h post-induction. Our study suggests that RTA might control the kinetics of viral replication through fine-tuning of the level of ORF45 and other viral/host proteins.
Coronaviruses (CoVs) have been studied for over 60 years, but have only recently gained notoriety as deadly human pathogens with the emergence of severe respiratory syndrome CoV and Middle East respiratory syndrome virus. The rapid emergence of these viruses has demonstrated the need for good models to study severe CoV respiratory infection and pathogenesis. There are, currently, different methods and models for the study of CoV disease. The available genetic methods for the study and evaluation of CoV genetics are reviewed here. There are several animal models, both mouse and alternative animals, for the study of severe CoV respiratory disease that have been examined, each with different pros and cons relative to the actual pathogenesis of the disease in humans. A current limitation of these models is that no animal model perfectly recapitulates the disease seen in humans. Through the review and analysis of the available disease models, investigators can employ the most appropriate available model to study various aspects of CoV pathogenesis and evaluate possible antiviral treatments that may potentially be successful in future treatment and prevention of severe CoV respiratory infections.
Introductions of H7 influenza A virus (IAV) from wild birds into poultry have been documented worldwide, resulting in varying degrees of morbidity and mortality. H7 IAV infection in domestic poultry has served as a source of human infection and disease. We report the detection of H7N9 subtype IAVs in Minnesota (MN) turkey farms during 2009 and 2011. The full genome was sequenced from eight isolates as well as the haemagglutinin (HA) and neuraminidase (NA) gene segments of H7 and N9 virus subtypes for 108 isolates from North American wild birds between 1986 and 2012. Through maximum-likelihood and coalescent phylogenetic analyses, we identified the recent H7 and N9 IAV ancestors of the turkey-origin H7N9 IAVs, estimated the time and geographical origin of the ancestral viruses, and determined the relatedness between the 2009 and 2011 turkey-origin H7N9 IAVs. Analyses supported that the 2009 and 2011 viruses were distantly related genetically, suggesting that the two outbreaks arose from independent introduction events from wild birds. Our findings further supported that the 2011 MN turkey-origin H7N9 virus was closely related to H7N9 IAVs isolated in poultry in Nebraska during the same year. Although the precise origin of the wild-bird donor of the turkey-origin H7N9 IAVs could not be determined, our findings suggested that, for both the NA and HA gene segments, the MN turkey-origin H7N9 viruses were related to viruses circulating in wild birds between 2006 and 2011 in the Mississippi Flyway.
The dengue virus (DENV) envelope protein domain 3 (ED3) is the target of potent virus neutralizing antibodies. The DENV-2 ED3 contains adjacent type-specific and DENV complex-reactive antigenic sites that are composed of a small number of residues that were previously demonstrated to be critical for antibody binding. Site-directed mutagenesis of a DENV-2 16681 infectious clone was used to mutate critical residues in the DENV-2 type-specific (K305A and P384A) and DENV complex-reactive (K310A) antigenic sites. The K305A mutant virus multiplied like the parent virus in mosquito and mammalian cells, as did the P384A mutant virus, which required a compensatory mutation (G330D) for viability. However, the K310A mutant virus could not be recovered. The DENV-2 type-specific critical residue mutations K305A and P384A+G330D reduced the ability of DENV-2 type-specific, but not DENV complex-reactive, mAbs to neutralize virus infectivity and this was directly correlated with mAb binding affinity to the rED3 mutants.
Infection of astrocytes by the neuropathogenic mutant of Moloney murine leukemia virus, ts1, exhibits increased levels of reactive oxygen species (ROS) and signs of oxidative stress compared with uninfected astrocytes. Previously, we have demonstrated that ts1 infection caused two separate events of ROS upregulation. The first upregulation occurs during early viral establishment in host cells and the second during the virus-mediated apoptotic process. In this study, we show that virus-mediated ROS upregulation activates the protein kinase, ataxia telangiectasia mutated, which in turn phosphorylates serine 15 on p53. This activation of p53 however, is unlikely associated with ts1-induced cell death. Rather p53 appears to be involved in suppressing intracellular ROS levels in astrocytes under oxidative stress. The activated p53 appears to delay retroviral gene expression by suppressing NADPH oxidase, a superoxide-producing enzyme. These results suggest that p53 plays a role as a retrovirus-mediated oxidative stress modulator.
Prions are amyloid-forming proteins that cause transmissible spongiform encephalopathies through a process involving the templated conversion of the normal cellular prion protein (PrPC) to a pathogenic misfolded conformation. Templated conversion has been modelled in several in vitro assays, including serial protein misfolding amplification, amyloid seeding and real-time quaking-induced conversion (RT-QuIC). As RT-QuIC measures formation of amyloid fibrils in real-time, it can be used to estimate the rate of seeded conversion. Here, we used samples from deer infected with chronic wasting disease (CWD) in RT-QuIC to show that serial dilution of prion seed was linearly related to the rate of amyloid formation over a range of 10−3 to 10−8 µg. We then used an amyloid formation rate standard curve derived from a bioassayed reference sample (CWD+ brain homogenate) to estimate the prion seed concentration and infectivity in tissues, body fluids and excreta. Using these methods, we estimated that urine and saliva from CWD-infected deer both contained 1–5 LD50 per 10 ml. Thus, over the 1–2 year course of an infection, a substantial environmental reservoir of CWD prion contamination accumulates.
The host and viral factors that influence disease outcome during flavivirus infections are not fully understood. Using the live attenuated yellow fever virus (YFV) vaccine strain 17D as a model system we evaluated how viral dose, inoculation route and immunopathogenesis contributed to disease outcome in mice deficient in the type I IFN response. We found that YFV-17D infection of IFN-α/β receptor knockout mice resulted in three distinct disease outcomes: no clinical signs of disease, fatal viscerotropic disease or fatal neurotropic disease. Interestingly, viral load at disease onset did not correlate with disease outcome. However, we found increased immune infiltrates in the brain tissues of mice that developed neurotropic disease. Additionally, mice that developed viscerotropic disease, as characterized by liver and spleen pathology and/or intestinal haemorrhage, had significantly elevated levels of alanine aminotransferase, monocyte chemotactic protein and IFN-inducible protein (IP)-10 as compared with mice with no clinical signs of disease or neurotropic disease. Furthermore, mice treated with recombinant IP-10 throughout YFV-17D infection showed increased mortality and an increased percentage of mice with viscerotropic disease. Our results demonstrated that viral load did not correlate with pathogenesis, and the host immune response played a pivotal role in disease outcome and contributed to YFV-17D pathogenesis in mice.
West Nile virus (WNV), an important global human pathogen, targets neurons to cause lethal encephalitis, primarily in elderly and immunocompromised patients. Currently, there are no approved therapeutic agents or vaccines to treat WNV encephalitis. Recent studies have suggested that inflammation is a major contributor to WNV encephalitis morbidity. In this study we evaluated the use of IVIG (intravenous immunoglobulins – a clinical product comprising pooled human IgG) as an anti-inflammatory treatment in a model of lethal WNV infection. We report here that IVIG and pooled human WNV convalescent sera (WNV-IVIG) inhibited development of lethal WNV encephalitis by suppressing central nervous system (CNS) infiltration by CD45high leukocytes. Pathogenic Ly6Chigh CD11b+ monocytes were the major infiltrating subset in the CNS of infected control mice, whereas IVIG profoundly reduced infiltration of these pathogenic Ly6Chigh monocytes into the CNS of infected mice. Interestingly, WNV-IVIG was more efficacious than IVIG in controlling CNS inflammation when mice were challenged with a high-dose inoculum (105 versus 104 p.f.u.) of WNV. Importantly, adsorption of WNV E-glycoprotein neutralizing antibodies did not abrogate IVIG protection, consistent with virus neutralization not being essential for IVIG protection. These findings confirmed the potent immunomodulatory activity of generic IVIG, and emphasized its potential as an effective immunotherapeutic drug for encephalitis and other virus induced inflammatory diseases.
CTLA-4 is a negative regulator of T-cell receptor-mediated CD4+ T-cell activation and function. Upregulation of CTLA-4 during human immunodeficiency virus type 1 (HIV-1) infection on activated T cells, particularly on HIV-specific CD4+ T cells, correlates with immune dysfunction and disease progression. As HIV-1 infects and replicates in activated CD4+ T cells, we investigated mechanisms by which HIV-1 modulates CTLA-4 expression to establish productive viral infection in these cells. Here, we demonstrate that HIV-1 infection in activated CD4+ T cells was followed by Nef-mediated downregulation of CTLA-4. This was associated with a decreased T-cell activation threshold and significant resistance to CTLA-4 triggering. In line with these in vitro results, quantification of pro-viral HIV DNA from treatment-naive HIV-infected subjects demonstrated a preferential infection of memory CD4+CTLA-4+ T cells, thus identifying CTLA-4 as a biomarker for HIV-infected cells in vivo. As transcriptionally active HIV-1 and Nef expression in vivo were previously shown to take place mainly in the CD3+CD4–CD8– [double-negative (DN)] cells, we further quantified HIV DNA in the CTLA-4+ and CTLA-4– subpopulations of these cells. Our results showed that DN T cells lacking CTLA-4 expression were enriched in HIV DNA compared with DN CTLA-4+ cells. Together, these results suggested that HIV-1 preferential infection of CD4+CTLA-4+ T cells in vivo was followed by Nef-mediated concomitant downregulation of both CD4 and CTLA-4 upon transition to productive infection. This also highlights the propensity of HIV-1 to evade restriction of the key negative immune regulator CTLA-4 on cell activation and viral replication, and therefore contributes to the overall HIV-1 pathogenesis.
During a hospital-based diarrhoeal disease study conducted in Ho Chi Minh City, Vietnam from 2009 to 2010, we identified four symptomatic children infected with G26P rotavirus (RV) – an atypical variant that has not previously been reported in human gastroenteritis. To determine the genetic structure and investigate the origin of this G26P strain, the whole genome of a representative example was characterized, revealing a novel genome constellation: G26–P–I5–R1–C1–M1–A8–N1–T1–E1–H1. The genome segments were most closely related to porcine (VP7, VP4, VP6 and NSP1) and Wa-like porcine RVs (VP1–3 and NSP2–5). We proposed that this G26P strain was the product of zoonotic transmission coupled with one or more reassortment events occurring in human and/or animal reservoirs. The identification of such strains has potential implications for vaccine efficacy in south-east Asia, and outlines the utility of whole-genome sequencing for studying RV diversity and zoonotic potential during disease surveillance.
Papillomaviruses are a family of slowly evolving DNA viruses and their evolution is commonly linked to that of their host species. However, whilst bovine papillomavirus-1 (BPV-1) primarily causes warts in its natural host, the cow, it can also cause locally aggressive and invasive skin tumours in equids, known as sarcoids, and thus provides a rare contemporary example of cross-species transmission of a papillomavirus. Here, we describe the first phylogenetic analysis of BPV-1 in equine sarcoids to our knowledge, allowing us to explore the evolutionary history of BPV-1 and investigate its cross-species association with equids. A phylogenetic analysis of the BPV-1 transcriptional promoter region (the long control region or LCR) was conducted on 15 bovine and 116 equine samples from four continents. Incorporating previous estimates for evolutionary rates in papillomavirus implied that the genetic diversity in the LCR variants was ancient and predated domestication of both equids and cattle. The phylogeny demonstrated geographical segregation into an ancestral group (African, South American and Australian samples), and a more recently derived, largely European clade. Whilst our data are consistent with BPV-1 originating in cattle, we found evidence of multiple, probably relatively recent, cross-species transmission events into horses. We also demonstrated the high prevalence of one particular sequence variant (variant 20), and suggest this may indicate that this variant shows a fitness advantage in equids. Although strong host specificity remains the norm in papillomaviruses, our results demonstrate that exceptions to this rule exist and can become epidemiologically relevant.
Vaccinia virus (VACV) is a large dsDNA virus encoding ~200 proteins, several of which inhibit apoptosis. Here, a comparative study of anti-apoptotic proteins N1, F1, B13 and Golgi anti-apoptotic protein (GAAP) in isolation and during viral infection is presented. VACVs strains engineered to lack each gene separately still blocked apoptosis to some degree because of functional redundancy provided by the other anti-apoptotic proteins. To overcome this redundancy, we inserted each gene separately into a VACV strain (vv811) that lacked all these anti-apoptotic proteins and that induced apoptosis efficiently during infection. Each protein was also expressed in cells using lentivirus vectors. In isolation, each VACV protein showed anti-apoptotic activity in response to specific stimuli, as measured by immunoblotting for cleaved poly(ADP ribose) polymerase-1 and caspase-3 activation. Of the proteins tested, B13 was the most potent inhibitor, blocking both intrinsic and extrinsic stimuli, whilst the activity of the other proteins was largely restricted to inhibition of intrinsic stimuli. In addition, B13 and F1 were effective blockers of apoptosis induced by vv811 infection. Finally, whilst differences in induction of apoptosis were barely detectable during infection with VACV strain Western Reserve compared with derivative viruses lacking individual anti-apoptotic genes, several of these proteins reduced activation of caspase-3 during infection by vv811 strains expressing these proteins. These results illustrated that vv811 was a useful tool to determine the role of VACV proteins during infection and that whilst all of these proteins have some anti-apoptotic activity, B13 was the most potent.
Human immunodeficiency virus type 2 (HIV-2) infects about two million people worldwide. HIV-2 has fewer treatment options than HIV-1, yet may evolve drug resistance more quickly. We have analysed several novel drugs for anti-HIV-2 activity. It was observed that 5-azacytidine, clofarabine, gemcitabine and resveratrol have potent anti-HIV-2 activity. The EC50 values for 5-azacytidine, clofarabine and resveratrol were found to be significantly lower with HIV-2 than with HIV-1. A time-of-addition assay was used to analyse the ability of these drugs to interfere with HIV-2 replication. Reverse transcription was the likely target for antiretroviral activity. Taken together, several novel drugs have been discovered to have activity against HIV-2. Based upon their known activities, these drugs may elicit enhanced HIV-2 mutagenesis and therefore be useful for inducing HIV-2 lethal mutagenesis. In addition, the data are consistent with HIV-2 reverse transcriptase being more sensitive than HIV-1 reverse transcriptase to dNTP pool alterations.
Despite the success of combined antiretroviral therapy in controlling viral replication in human immunodeficiency virus (HIV)-infected individuals, HIV-associated neurocognitive disorders, commonly referred to as neuroAIDS, remain a frequent and poorly understood complication. Infection of CD8+ lymphocyte-depleted rhesus macaques with the SIVmac251 viral swarm is a well-established rapid disease model of neuroAIDS that has provided critical insight into HIV-1-associated neurocognitive disorder onset and progression. However, no studies so far have characterized in depth the relationship between intra-host viral evolution and pathogenesis in this model. Simian immunodeficiency virus (SIV) env gp120 sequences were obtained from six infected animals. Sequences were sampled longitudinally from several lymphoid and non-lymphoid tissues, including individual lobes within the brain at necropsy, for four macaques; two animals were sacrificed at 21 days post-infection (p.i.) to evaluate early viral seeding of the brain. Bayesian phylodynamic and phylogeographic analyses of the sequence data were used to ascertain viral population dynamics and gene flow between peripheral and brain tissues, respectively. A steady increase in viral effective population size, with a peak occurring at ~50–80 days p.i., was observed across all longitudinally monitored macaques. Phylogeographic analysis indicated continual viral seeding of the brain from several peripheral tissues throughout infection, with the last migration event before terminal illness occurring in all macaques from cells within the bone marrow. The results strongly supported the role of infected bone marrow cells in HIV/SIV neuropathogenesis. In addition, our work demonstrated the applicability of Bayesian phylogeography to intra-host studies in order to assess the interplay between viral evolution and pathogenesis.
Rats are known as reservoirs and vectors for several zoonotic pathogens. However, information on the viruses shed by urban wild rats that could pose a zoonotic risk to human health is scare. Here, intestinal contents from 20 wild Norway rats (Rattus norvegicus) collected in the city of Berlin, Germany, were subjected to metagenomic analysis of viral nucleic acids. The determined faecal viromes of rats consisted of a variety of known and unknown viruses, and were highly variable among the individuals. Members of the families Parvoviridae and Picobirnaviridae represented the most abundant species. Novel picornaviruses, bocaviruses, sapoviruses and stool-associated circular ssDNA viruses were identified, which showed only low sequence identity to known representatives of the corresponding taxa. In addition, noroviruses and rotaviruses were detected as potential zoonotic gastroenteritis viruses. However, partial-genome sequence analyses indicated that the norovirus was closely related to the recently identified rat norovirus and the rotavirus B was closely related to the rat rotavirus strain IDIR; both viruses clustered separately from respective human virus strains in phylogenetic trees. In contrast, the rotavirus A sequences showed high identity to human and animal strains. Analysis of the nearly complete genome of this virus revealed the known genotypes G3, P and N2 for three of the genome segments, whereas the remaining eight genome segments represented the novel genotypes I20–R11–C11–M10–A22–T14–E18–H13. Our results indicated a high heterogeneity of enteric viruses present in urban wild rats; their ability to be transmitted to humans remains to be assessed in the future.
Laboratory animal models have provided valuable insight into foot-and-mouth disease virus (FMDV) pathogenesis in epidemiologically important target species. While not perfect, these models have delivered an accelerated time frame to characterize the immune responses in natural hosts and a platform to evaluate therapeutics and vaccine candidates at a reduced cost. Further expansion of these models in mice has allowed access to genetic mutations not available for target species, providing a powerful and versatile experimental system to interrogate the immune response to FMDV and to target more expensive studies in natural hosts. The purpose of this review is to describe commonly used FMDV infection models in laboratory animals and to cite examples of when these models have failed or successfully provided insight relevant for target species, with an emphasis on natural and vaccine-induced immunity.